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large multi-touch screen panel
May 31, 2018

According to Business Research's 2015 global touch screen market report, projection capacitor (P-CAP) technology has occupied the highest number of touch categories for mobile phones and tablets since 2009. The driving force of this success is a compelling set of functions, including the effective unlimited service life achieved through the durable glass surface, the full graphic design of the printed border (without the need for a light ring) and the advanced sensitivity. P-CAP manufacturers are currently using this technology on the largest 85 "screen. They focus on four areas to promote touch performance and user interface design. They are speed, precision, anti EMI and integration.

Let's look at a picture below.

The above is the outdoor touch panel on the Seoul bus station with 8 millimeter protection glass under the average summer temperature of 29 C in summer and the low temperature of 7.3 C in the winter level, so the touch panel is still working properly. So a large touch screen touch IC must support thick panels, and then withstand the harsh outdoor environment.

The above image is located at the Kite GB flagship store in London's London fashion high street, the pioneering, touttouch experience and networking product that uses the 42 "touch panel of Zytronic integrated glass strengthening."

The improvement against EMI

Although electromagnetic interference (EMI) may be only a touch screen system in an industrial environment, in fact, various commercial applications of EMI may also have an adverse impact on touch operation. For example, when the train passes by, the self-service kiosks such as ticketing and vending machines will be affected by the surge in EMI. Similarly, touch screens deployed in unstable or poorly regulated areas will also be affected by the instantaneous interference of the main power cables.

In particular, the 4K display currently generates higher EMI because of the complexity of driving circuit needed to manage higher pixel density. This leads to the interference or "noise" of the display screen at most 3~4 times higher than that of the ordinary HD display. It causes the touch screen and their control electronic components to determine the signal (or touch) from the surrounding noise, that is, to reduce the signal to noise ratio and thus weaken the recognition of real touch events.

The main improvement of the electronic design and touch detection firmware for the touch controller deployed in these environments is to ensure signal integrity at a high level. P-CAP touch technology, such as the exclusive projection capacitive Technology (PCT) of Zytronic, has a X-Y matrix with a fine electrode, embedded in a layered glass substrate, and uses frequency modulation to detect the minute capacitance changes in the conductive electrode. One way to combat EMI is to perform "intelligent" frequency scanning in touch controllers. The operation frequency moves dynamically between 0.7MHz and 2.2MHz to avoid detection of environmental "noise" to prevent detection of touch events.

Better integration

Although the touch kiosk is a fairly large device, it is usually surprising that the small space behind the screen provides aesthetic requirements and other elements so that it is sometimes needed to be incorporated into the device. If the volume of the touch controller can be kept minimal, it has obvious advantages.  Therefore, it is important to reduce the size of PCB, so that the controller becomes a chip set product so that the designer can consider the touch controller to be embedded on the existing system motherboard.

high sensitivity

Basically, the key contribution of P-CAP touch technology, such as PCT and MCPT, is its high sensitivity. It can detect touch through super thick overlapping layer, protective glass or even thick gloves, so it has an incomparable Z axis sensitivity and control level. With a well designed touch controller, it provides a reliable and intuitive touch experience, accurate response to up to 40 touches, recognition of postures and rejection of accidental contact. The continuous improvement of the P-CAP controller IC combined with the development of sensors for print sensing ink and nanomaterials, and may further expand the function and use of this general touch technology series.

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